The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Internal combustion engines combust an air/fuel mixture to produce drive torque. Air is drawn into an engine through an intake manifold. A throttle valve controls airflow into the engine. The air mixes with fuel injected by one or more fuel injectors to form the air/fuel mixture. The air/fuel mixture is combusted within one or more cylinders of the engine. Combustion of the air/fuel mixture generates drive torque.
Exhaust resulting from the combustion of the air/fuel mixture includes particulate matter (PM) and exhaust gas. The exhaust gas includes nitrogen oxides (NOx), such as nitrogen monoxide (NO) and nitrogen dioxide (NO2). The PM may include hydrocarbons and carbon oxides. The exhaust is expelled from the engine to an exhaust system that includes a treatment system. The treatment system reduces the amounts of NOx and PM in the exhaust.
The treatment system includes an oxidation catalyst (OC), a dosing agent injector, a selective catalytic reduction (SCR) catalyst, and a particulate filter (PF). The OC removes (e.g., combusts) hydrocarbons and/or carbon oxides from the exhaust. The dosing agent injector injects a dosing agent into the exhaust stream at a location between the OC and the SCR catalyst. The SCR catalyst absorbs ammonia (NH3) provided by the dosing agent, and the NH3 reacts with NOx in the exhaust.